The method of lightning protection which is the oldest as well of the longest length of service dating back two hundred years employs a Franklin rod to collect, control, and convey to earth the awesome and destructive power of lightning. The side effects of allowing thousands of amperes to flow adjacent to and near computers and sensitive electronic equipment can be very costly and undesirable in the advanced technological arena which we now have to protect from lightning. Changes, which have occurred in lightning protection technology, include the renewed debate over sharp pointed versus blunt rods. A further discussion of sharp pointed versus blunt rods has been given in papers by Donald W. Zipse, P. E. Life Fellow, IEEE Titled: xe2x80x9cLightning Protection Methods: An Update And A Discredited System Vindicatedxe2x80x9d which appears in: Industrial and Commercial Power Systems Technical Conference, 2000, Conference Record, and 2000 IEEE, dated May 7-11, 2000. This update includes a reference to an earlier paper by Zipse Titled: xe2x80x9cLightning Protection Systems: Advantages and Disadvantagesxe2x80x9d which appeared in IEEE PCIC Conference Record, 1993, pp.51-64, Sep. 13, 1993. The historical and pertinent discussions taken from this referenced paper is set forth below to provide a better understanding of this portion of prior art.
xe2x80x9cFranklin chose the sharp pointed rod over the blunt rod to intercept the lightning stroke and transfer the electric charge to earth. Disagreement originated in England with King George III who installed blunt rods in the belief that sharpened rods would attract lightning.xe2x80x9d
Franklin in experimenting discovered that a sharp iron rod could easily and silently conducts electricity from charged metal spheres. Sharp rods, he theorized, elevated and connected to the earth, could discharge the electricity in thunderclouds. Later, Franklin determined if sharp rods did not discharge the overhead thundercloud, blunt rods would intercept the lightning, strike, shielding the nearby building from danger. The two-prong approach had support; however, further experimentation showed rods with knobs on them would attract a lightning stroke from a greater distance than a pointed rod. The use of blunt rods were favored by King George III who equipped his palace with blunt rods. He felt that sharpened rods might attract lightning and thus promote the mischief that it was hoped to prevent. The Royal Naval adopted blunt rods and incidents of wooden masts being struck were reduced.
Lightning interception systems have included the cone of protection technique and the rolling ball technique. Other techniques exist. One is considered the modified rolling ball technique and the other is hemispheres and collection volumes. Each of these techniques will be briefly discussed below to provide a better understanding of the efforts over the years to better control lightning.
The area of protection that a vertical lightning rod would cover would be that area which is defined in the angle from the tip of the rod to a distance on the ground equal to the height of the rod, a 45xc2x0 angle. This area under the straight line from the rod tip to the ground is called the xe2x80x9czone of protectionxe2x80x9d. Over time, the angle has been changed to 60xc2x0 to afford a higher degree of reliability. It has been determined that negative lightning leaders advance in discrete steps of up to 45.7 m (150 feet) as it advances from cloud to earth. When the leader is within 45.7 m (150 feet) of the earth, the leader will be attracted to an object. This explains why a tall structure is struck below the top. This led to a new concept in the late 1970""s, the rolling ball concept.
In the rolling ball concept one needs to visualize a sphere of 150 radiuses and roll this ball over the surface of the earth. Where the surfaces of the ball rest on two protruding projections, everything under the surface of the ball would be protected.
As the advanced state of the art has progressed in the last four decades due to the explosive progress in computers/electronics technology, the secondary effect of the lightning stroke became the major concern in many cases. Thus, during the past 250 years lightning rod successfully protected structures from the lightning-caused damage. As noted the secondary effect produced by lightning current which comprise the strong magnetic field around the downward conductor connecting the lightning rod to the grounding system induces voltages of such magnitude that they are capable to cause permanent damage or cause malfunction of sensitive electronic equipment located nearby.
More recently, efforts to replace the conventional lightning rod by a Charge Transfer System (CTS) has improved significantly the lightning protection of structures against direct lightning strokes. The typical CTS consist of four major parts: an ionizer, a grounding system, a ground current collector, and a grounding conductor connecting the ionizer to the grounding system. The CTS system during the recent thirty years has included systems designated as Dissipation Array System (DAS), the Spline Ball Ionizer and Spline Ball Terminal (SBI and SBT), the Ion Plasma Generator (IPG), etc. The CTS system offers much larger area of protection against direct lightning strokes comparing with the performance of the lightning rod. Working in the stroke prevention mode the CTS system also reduces significantly the secondary effect of the lightning stroke.
Prior art method for triggering lightning involves launching a small rocket trailing a thin grounded wire toward a charged cloud overhead. The cloud charge is indirectly sensed by measuring the electric field at ground, values of 4 to 10 kV/m generally being good indicators of favorable conditions for lightning initiation. When the rocket, ascending at about 200 m/s, is about 200 to 300 m high, the field enhancement near the rocket tip launches a positively charged (for the common summer thunderstorm having predominantly negative charge at 5 to 7 km altitude) leader that propagates upward toward the cloud. This leader vaporizes the trailing wire and initiates a so called xe2x80x9cinitial continuous currentxe2x80x9d of the order of several hundred amperes flowing from the cloud charge source to the top of the wire residue and further along the wire trace to the instrumental triggering facility. The firing of the rocket motor takes place when the field strength reaches the favorable value mentioned above. state of the art electronic equipment when the proper static charge is detected for potential a lightning strike.
Thus triggering lightning flashes with a rocket system employs typically a one meter long solid fuel rocket and a 0.2 mm diameter copper wire which unspools behind the rocket. The trailing wire serves in the capacity of a grounding conductor connecting the ionizer to the grounding system. When the rocket reaches sufficient altitude, a flash is triggered down the wire quickly vaporizing the wire. The vaporized wire leaves a conductive path to the grounding system. In the event that the wire does not get vaporized because of failure of the trailing wire to intercept the static charge in the storm cloud, a hazard could result whereby the falling wire could fall over transmission lines thereby causing shorting.
An object of this invention is to provide a non-wire path of conductive material to create a controlled conductive path from ground to the static charge at a given time so that the charge is neutralized.
A further object of this invention is to provide a rocket, which is composed, of materials, which produce a minimum of falling-mass hazards after the rocket, is exhausted.
This invention comprises a device, which is designed to control the time and the location of a lightning strike. By such control the adverse effects of lightning on equipment and property can be minimized or eliminated.
A means for creating a controlled conductive path from ground to the static charge of a storm cloud achieves neutralization of the static charge at a given time and in a controlled manner to thereby minimize or eliminate the damage of a lightning strike.
A rocket motor case and components are provided which are made of cloth such as used in airbags or thin plastic such as polystyrene or polypropylene which is used in drink bottles. The rocket motor itself when exhausted is thus composed of materials, which produce a minimum of falling-hazards. The propellant of the rocket motor includes additives of salts and compounds, which produce an ionized path for the static discharge to travel to the launch site. Such additives can include (but not limited to) cesium salts, sodium chloride, or small metallic particles.
The rocket operates at a relative low pressure, and low velocity thereby minimizing the inert mass. The rocket can be strategically placed in urban or remote area. The rocket launcher is placed on the ground and additionally serves as the ground discharge point to which the controlled conductive exhaust gases directs the lightning discharge. The system device remains passive until a lightning storm or high potential of lightning is present. Detection devices to measure the presence of electrostatic and ionic charge are placed in close proximity to the rocket launcher, which also fires the rocket. Adjustment to differing charge levels can be made in order to have multiple firing in close proximity to each other.